Author: Gerd Isenberg
Date: 12:54:40 09/15/04
Go up one level in this thread
On September 15, 2004 at 15:11:35, Robert Hyatt wrote: >On September 15, 2004 at 14:48:51, Gerd Isenberg wrote: > >>On September 15, 2004 at 12:17:14, Robert Hyatt wrote: >> >>>On September 15, 2004 at 09:53:53, Stuart Cracraft wrote: >>> >>>>Hi, >>>> >>>>Anyone know of some code somewhere that implements >>>>at least part (or all) of the originally described >>>>singular extension and/or any modifications to it that >>>>have proven worthwhile (if any)? >>>> >>>>I am curious what mediocre (or better) results people >>>>have gotten with singular extension. Originally Anantharaman >>>>hypothesized that it wouldn't be good at the slower >>>>speeds of most programs at the time and would require >>>>fast speeds to show effect. Has this proven true or >>>>false in the intervening 15 years? >>>> >>>>Is singular extension now generally discredited as a >>>>non-reproducible singularity in and of itself? >>>> >>>>Thanks, >>>> >>>>Stuart >>> >>> >>>It worked in Cray Blitz for the last two years it competed. How much it >>>improves overall chess skill is debatable. Early on the DB guys claimed very >>>significant improvements. Later more thorough testing showed that there was >>>definitely an improvement, but not as large as originally thought. >>> >>>I have not really spent a lot of time doing this in Crafty although there is a >>>SE version roaming around that I released, but it didn't do SE like the DB guys >>>did. Their implementation is not a 2 week deal. Expect to spend a year getting >>>it working as they did, if not more. >>> >>>Some commercial programs use variants. IE Wchess used the PV-singular part of >>>singular extensions, but not the fail-high part the DB guys defined. >> >>There are so many applications of a reduced/modified pre-search to gain more >>informations for better move sorting, pruning, extensions and reductions. >> >>1. Internal iterative deepening >>2. Nullmove oberservation or pre-verification >>3. Looking for singularity >>4. Looking for multiple beta cuts >> >>I wonder whether there is an approach to combine a few of them on cut-nodes. > >Hsu's paper defined singular extensiosn for PV nodes and CUT nodes. His paper >said "we have found no useful definition for a singular move at an ALL node >however.." Hmm isn't the definition simply that there is one move which is by a certain amount better than all others, independent on pv-, cut- and all-node? Probably the forced situation, that there is only _one_ move (e.g. becomes alpha while all others are less alpha-margin), makes it worth to look deeper to look whether the all-node becomes a singular cut node or improves alpha, with possible influence at the root. > > >> >>Btw. considering minimal tree node types, pv-, cut- and all nodes >>(pv most left, cut successor from pv or all, all successor from cut) >>What information may we gain, for a cut node, where only one successor has to be >>searched in a minimal tree, if it behaves like an all node? > >All I can immediately think of is that your move ordering is bad at that CUT >node, because by definition you only need to search 1 move at a CUT node, and >not even the best move, just one "good enough to produce a cutoff." Yes, but even considering rather perfect move ordering it should happen in practice - otherwise you will never found a better move at the root. I'm interested in some statistics, how often cut-nodes behave all-like (eval fails, first fails, all fail), same for all nodes with cuts and this correlates with branching factor - and the influence of several move ordering heuristics. Hmm, is it worth to update node types incrementally during search? I guess with a counter of played pv-moves (0..N) in the top of the current path and ply index one may determine the minimal tree node type as well... So we have distance D of the current node to the last pv node in the current path. If D == zero we have a pv-node. If D is odd we have a cut node. If D is even and greater zero we have an all node. > >>E.g. if static eval <= alpha or even first move doesn't improve alpha? >> >>Thanks, >>Gerd
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